In devices which perform a desired operation by transmitting input torque from a rotational driving source such as a motor to an output mechanism, when the driving source is stopped, there are occasions in which it is desirable to block the transmission of reverse input torque from the output mechanism back to the input side.
An example of such an occasion is when a retention function is employed to prevent the position of the output mechanism fluctuating when the driving source is stopped. In this type of device, taking an electric shutter as an example, the input torque from the driving motor in either a forward or reverse direction is input to an opening and closing mechanism on the output side, which then performs the operation for either opening or closing the shutter, although if for some reason (such as a power failure or the like) the driving motor is stopped partway through the opening or closing operation, reverse input torque resulting from the descent of the shutter under its own weight is returned to the input side, resulting in the possibility of damage to the input side components. Consequently, a mechanism is required which holds the position of the shutter, and prevents the return of reverse input torque from the shutter to the input side.
Furthermore, in a construction in which a reduction gear is used to reduce the revolutions of a motor, the following problems may arise in those cases where, for some reason, torque is reverse input from the output side.
(a) In a case in which worm gearing is used as the reduction gear, then because rotation under reverse input is impossible with this type of worm gearing, a very large load is exerted on the worm wheel or the teeth of the worm. In particular, a very large thrust loading acts upon the worm. As a result, there is a danger of damage to the bearing supporting the teeth and the worm, or alternatively, the mechanism must be increased in size in order to prevent this type of damage.
(b) Even in the case of a reduction gear which utilizes a spur gear or a helical gear, there is still a possibility of damage to the teeth in those cases where the reverse input torque becomes excessively large (such as the case of a shocking reverse input).
In order to resolve the problems outlined above, a mechanism is required which is capable of transmitting input torque from the motor of the input side to the output side, but also capable of locking the output side with respect to reverse input torque from the output side, thereby preventing the return of reverse input torque to the motor or the reduction gear on the input side.
Furthermore in recent years, many vehicles including automobiles hive been equipped with motor driven electric retractable door mirrors, wherein the mirror moves through an angle of approximately 90xc2x0 between a working position in which the mirror protrudes out from the side of the vehicle, and a retracted storage position. A conventional electric retractable door mirror (such as that disclosed in Japanese Patent Laid-Open Publication No. Hei 11-51092) utilizes a driving mechanism such as that shown in FIG. 29, wherein a mirror 42 can be moved easily by driving a motor 41, but when an external force acts upon the mirror 42, a clutch 43 effectively blocks the external force, holding the mirror 42 firmly in place and preventing the external force from acting upon the motor 41.
However, in the driving mechanism disclosed in the above publication, because the mirror is securely fixed and undergoes no rotation even if an external force results in a reverse input torque acting upon the mirror, the mechanism is unable to absorb such an external force, and the mirror is consequently prone to damage. In order to resolve this problem, a mechanism is required which is capable of transmitting input torque from the motor of the input side to the mirror of the output side, but also permits the mirror to slip with respect to reverse input torque, thereby blocking the transmission of such reverse input torque back to the input side.
An object of the present invention is to provide a reverse input blocking clutch which has the functions described above, and yet is compact, lightweight and low cost, as well as a clutch device using such a reverse input blocking clutch.
In order to achieve this object, a reverse input blocking clutch of the present invention comprises an input member into which torque is input, an output member to which torque is output, a stationary member for constraining the revolutions, locking means provided between the stationary member and the output member for locking the output member and the stationary member with respect to reverse input torque from the output member, lock release means provided on the input member for releasing a locked state produced by the locking means with respect to input torque from the input member, and torque transmission means provided between the input member and the output member for transmitting input torque from the input member to the output member when the locked state produced by the locking means is released, wherein at least the input member from amongst the input member, the output member and the stationary member is produced by deformation processing of a metal plate.
The xe2x80x9clocking meansxe2x80x9d described above incorporates a device which applies an antirotation force by means of a wedge engagement force, an engagement between concave and convex surfaces, frictional force, magnetic force, electromagnetic force, fluid pressure, fluid viscosity resistance or a fine particle medium or the like, although from the viewpoints of cost, the simplicity of the structure and the control mechanism, and the smoothness of operation a device which applies an antirotation force by means of a wedge engagement force is preferred. Specifically, a wedge shaped gap is formed between the output member and the stationary member, and an engagement member is then either engaged into, or disengaged from this gap to switch the device between a locked state and a slipping state respectively. Furthermore, this type of construction includes Structures in which a cam surface for forming the wedge shaped gap is provided on either the output member or the stationary member (and an engagement member with a circular cross section such as a roller or a ball is used), and structures in which a cam surface for forming the wedge shaped gap is provided on the engagement member (and a sprag or the like is used as the engagement member).
Furthermore, the xe2x80x9cmetal platexe2x80x9d described above may be any metal plate capable of being shaped by deformation processing to the desired shape and dimensions. There are no particular restrictions on the material used, and a steel plate is a suitable example. Furthermore, the deformation processing can utilize techniques such as press working.
According to the above construction, when input torque is input at the input member, first the locked state produced by the locking means is released by the lock release means, and with the device in this released state, the input torque from the input member is transmitted to the output member via the torque transmission means. In contrast, a reverse input torque from the output member is locked between the output member and the stationary member by the locking means. Accordingly, a function is achieved wherein input torque from the input side is transmitted to the output side, whereas reverse input torque from the output side is not returned to the input side. Furthermore, by producing at least the input member from amongst the input member, the output member and the stationary member, from a metal plate which has undergone deformation processing, then in comparison with forged products, cast products or cutout products, the device is more compact, lighter, and cheaper to produce.
In the above construction, a connector can be provided for connecting an input shaft to the input member, and this connector can be positioned inside the clutch. As a result, the dimensions of the clutch itself in an axial direction can be kept compact, and furthermore the overall dimensions in an axial direction upon assembly with the rotational driving source can also be kept compact. This connector is preferably provided on a cylindrical section which extends in a continuous manner from the inner perimeter of the input member towards the inside of the clutch, and is also provided with at least one flat surface section which engages with a flat surface on the input shaft. This engagement between the flat surface of the input shaft and the flat surface of the connector causes the input shaft and the input member to be connected in such a manner that prevents relative rotation.
Furthermore in the above construction, a cylindrical output shaft section can also be incorporated into the output member. By so doing, the weight of the output shaft section can be reduced, the number of components can be reduced, and the production cost can be lowered. The output shaft section should preferably be closed at one end. By so doing, the strength of the output shaft section relative to a radial load or a torsional torque can be increased, and so deformation can be prevented and durability improved. Furthermore, the output shaft section should also preferably comprise at least one flat surface which engages,.with a flat surface of another driven member (a rotating member of a mechanism or device connected to the output side). The engagement between the flat surface provided on this other driven member and the flat surface of the output shaft section causes the output shaft section and the other driven member to be connected in such a manner that prevents relative rotation. Alternatively, a spline section or a serrated section which engages with a corresponding section on the other driven member could also be provided on the output shaft section.
In the above construction, the locking means can comprise a circumferential surface provided on the stationary member, a cam surface provided on the output member for forming the wedge shaped gap in the directions of both forward and reverse rotation between the output member and the circumferential surface, a pair of engagement members positioned between the cam surface and the circumferential surface, and an elastic member for pressing the pair of engagement members in the direction of the wedge shaped gap, the lock release means can be an engagement element which engages with either one of the pair of engagement members and pushes that engagement member in a direction away from the wedge shaped gap, and the torque transmission means can comprise rotational engagement elements provided on the input member and the output member, wherein at the neutral positions of the lock release means and the torque transmission means, the gap xcex41 in the direction of rotation between the engagement element of the lock release means and the engagement member, and the gap xcex42 in the direction of rotation between the engagement elements of the torque transmission means exist in a relationship in which xcex41 less than xcex42.
According to the above construction, when a reverse input torque of one direction is input at the output member, one of the pair of engagement members engages in the wedge shaped gap in that direction, and the output member is locked in that direction relative to the stationary member. In contrast, when a reverse input torque of the other direction is input at the output member, the other one of the pair of engagement members engages in the wedge shaped gap in that direction, and the output member is locked in the other direction relative to the stationary member. Consequently, the output member is locked in both the forward and reverse rotational directions relative to the stationary member by the actions oh the pair of engagement members. In contrast, when input torque is input at the input member, first the engagement element provided as the lock release means on the input member pushes the engagement member which engages with the wedge shaped gap in the direction of the torque away from the wedge shaped gap, disengaging the engagement member from the wedge shaped gap. As a result, the locked state of the output member is released relative to the direction of the input torque. Subsequently, with the output member in this released state, the rotational engagement elements provided on the input member and the output member as the torque transmission means engage with one another. By so doing, the input torque input at the input member is transmitted from the input member to the torque transmission means (the rotational engagement elements) and through to the output member, causing the output member to rotate.
By setting the relationship between the gap xcex41 in the direction of rotation between the engagement element of the lock release means and the engagement member, and the gap xcex42 in the direction of rotation between the engagement elements of the torque transmission means, so that at the neutral positions of the lock release means and the torque transmission means xcex41 less than xcex42, the lock release process provided by the aforementioned lock release means and the torque transmission process provided by the torque transmission means can be carried out consecutively and reliably.
In the above construction, the torque transmission means may comprise a convex section provided on either one of the input member and the output member, and a matching concave section provided on the other member. Specifically, a protrusion comprising the convex section can be provided on the output member, and a notch or a cavity comprising the concave section provided on the input member. In such a case, the protrusion may either protrude out in a radial direction or in an axial direction. Moreover, the cam surface may be formed directly on the output member, or alternatively a separate member with a cam surface may be attached to the output member. Furthermore, a roller should preferably be used as the engagement member.
In the above construction, the aforementioned elastic member could comprise a base and a tongue section extending from the base in either one of the axial directions, wherein the tongue section is positioned between the pair of engagement members and pushes the pair of engagement members mutually apart. The elastic member should preferably comprise an integrated ring, namely, a ring shaped base with a plurality of tongues positioned around the circumference of the ring, as such a structure enables a reduction in the number of components, and a consequent lowering of the production cost.
In the above construction, a fixed side plate can be fixed to the stationary member, with this fixed side plate produced from a metal plate which has undergone deformation processing. In such a case, the bearing supporting the input shaft in a radial direction can be integrated into this fixed side plate. As a result, the operation of rotating the input shaft and the input member can be performed smoothly and with good stability, and the application of an unbalanced load to the locking means can be prevented or suppressed, thereby enabling a more stable clutch operation. Moreover, although this bearing may also be constructed by providing a separate rolling bearing or sliding bearing, the integrated structure described above enables a simpler structure and a reduced number of components. This bearing should preferably be provided on a cylindrical section extending in a continuous manner from the inner perimeter of the fixed side plate towards the inside of the clutch.
Furthermore in order to resolve the problems described above, a clutch device of the present invention is an integrated unit comprising a rotational driving source and a reverse input blocking clutch. The reverse input blocking clutch comprises an input member into which torque from the rotational driving source is input, an output member to which torque is output, a stationary member for constraining the revolutions, locking means provided between the stationary member and the output member for locking the output member and the stationary member with respect to reverse input torque from the output member, lock release means provided on the input member for releasing a locked state produced by the locking means with respect to input torque from the input member, and torque transmission means for transmitting input torque from the input member to the output member when the locked state produced by the locking means is released.
According to the above construction, when input torque from the rotational driving source is input at the input member of the reverse input blocking clutch, first the locked state produced by the locking means is released by the lock release means, and with the device in this released state, the input torque from the input member is transmitted to the output member via the torque transmission means. In contrast, a reverse input torque from the output member is locked between the output member and the stationary member by the locking means. Accordingly, a function is achieved wherein input torque from the input side is transmitted to the output side, whereas reverse input torque from the output side is not returned to the rotational driving source of the input side. Furthermore, by producing this reverse input clutch as an integrated unit with the rotational driving source, the deleterious effects of reverse input torque on the rotational driving source can be avoided, and a clutch device (rotational driving device) can be provided which is lightweight, compact, and cheap to produce.
Furthermore, the same effects can be achieved with an integrated clutch device (rotational driven device) comprising (1) a reverse input blocking clutch comprising an input member into which torque from the rotational driving source is input, an output member to which torque is output, a stationary member for constraining the revolutions, locking means provided between the stationary member and the output member for locking the output member and the stationary member with respect to reverse input torque from the output member, lock release means provided on the input member for releasing a locked state produced by the locking means with respect to input torque from the input member, and torque transmission means for transmitting input torque from the input member to the output member when the locked state produced by the locking means is released, and (2) an output mechanism for performing a desired operation using the torque transmitted to the output member of the reverse input blocking clutch.
What is described above as a xe2x80x9crotational driving sourcexe2x80x9d refers to a device for generating rotational torque, and includes motors, engines, and hand operated members such as handles, as well as combinations of such devices with reduction gears.
Furthermore, by producing at least the input member from amongst the input member, the output member and the stationary member of the reverse input blocking clutch, from a metal plate which has undergone deformation processing, then in comparison with forged products, cast products or cutout products, the device is more compact, lighter, and cheaper to produce.
In the above construction, a connector can be provided for connecting an output shaft of the rotational driving source to the input member, and this connector can be positioned inside the clutch. As a result, the dimensions of the clutch itself in an axial direction can be kept compact, and furthermore the overall dimensions of the aforementioned clutch device in an axial direction can also be kept compact. This connector is preferably provided on a cylindrical section which extends in a continuous manner from the inner perimeter of the input member towards the inside of the clutch, and is also provided with at least one flat surface section which engages with a flat surface on the output shaft of the rotational driving source. This engagement between the flat surface provided on the output shaft of the rotational driving source and the flat surface of the connector causes the output shaft and the input member to be connected in such a manner that prevents relative rotation.
Furthermore, at least one flat surface which engages with a flat surface of a driven member of an output mechanism may also be provided on the output shaft section. The engagement between the flat surface provided on this driven member and the flat surface of the output shaft section causes the output shaft and the other driven member to be connected in such a manner that prevents relative rotation. Alternatively, a spline section or a serrated section which engages with a corresponding section on the driven member of the output mechanism could also be provided on the output shaft section.
In the above construction, the locking means of the reverse input blocking clutch comprises a circumferential surface provided on the stationary member, a cam surface provided on the output member for forming a wedge shaped gap in the directions of both forward and reverse rotation between the output member and the circumferential surface, a pair of engagement members positioned between the cam surface and the circumferential surface, and an elastic member for pressing the pair of engagement members in the direction of the wedge shaped gap. The lock release means is an engagement element which engages with either one of the pair of engagement members and pushes that engagement member in a direction away from the wedge shaped gap, and the torque transmission means comprises rotational engagement elements provided on the input member and the output member. At the neutral positions of the lock release means and the torque transmission means, the gap xcex41 in the direction of rotation between the engagement element of the lock release means and the engagement member, and the gap xcex42 in the direction of rotation between the engagement elements of the torque transmission means exist in a relationship in which xcex41 less than xcex42.
Furthermore, in order to resolve the problems described above, a clutch device according to the present invention is a device for moving a driven member between at least two predetermined prescribed positions, incorporating a rotational driving source, a reverse input blocking clutch comprising an input member into which torque from the rotational driving source is input, and an output member connected to the driven member, for transmitting input torque applied to the input member to the output member, while blocking the transmission of reverse input torque applied at the output member to the input member and permitting the slipping of the output member, and restraining means for elastically restraining the rotation of the output member at each of the prescribed positions
According to such a construction, input torque applied from the rotational driving source to the input member is transmitted to the output member of the reverse input blocking clutch, and this rotational torque causes the driven member to move between the two (or three or more) prescribed positions. When the driven member reaches each prescribed position, the rotation of the output member is restrained elastically by the restraining means, and so the driven member resists external forces and is retained in that position. However, if the external force becomes very large and the reverse input torque reaches a level exceeding the elastic rotational restraining force of the restraining means, then the output member overcomes this rotational restraining force and begins to rotate. Here, because the reverse input blocking clutch is of a construction which permits the slipping of the output member relative to reverse input torque, this slipping of the output member enables the driven member to be freely rotated, and this free rotation in turn enables the absorption of the external force acting upon the driven member. Furthermore, because the reverse input blocking clutch blocks the transmission of reverse input torque to the input member, damage to the rotational driving source resulting from large reverse input torque can be prevented.
In addition, the reverse input blocking clutch may also comprise a torque transmission member which can be engaged with and disengaged from the input member and the output member in the directions of both forward and reverse rotation, a retainer for retaining the torque transmission member and controlling the engagement and disengagement of the torque transmission member through relative rotation relative to the input member, a first elastic member for connecting the input member and the retainer in a rotational direction, a stationary member, and rotational resistance application means for applying sliding frictional resistance to the retainer for rotation of the retainer relative to the stationary member.
According to the above construction, when rotational torque from the rotational driving source is input at the input member of the reverse input blocking clutch, the input member and the retainer connected to the input member begin to rotate via the first elastic member. Accompanying this rotation, a sliding frictional resistance acts upon the retainer due to the action of the rotational resistance application means, and consequently the retainer is subject to rotational resistance and develops a rotational lag, undergoing relative rotation with respect to the input member (at this point, the first elastic member is subject to elastic deformation). With the retainer in this state of rotational lag, the torque transmission member engages with both the input member and the output member, and the rotational torque input at the input member is transmitted to the output member via the torque transmission member.
In contrast, sliding frictional resistance from the rotational resistance application means does not act upon the retainer with respect to rotational torque input from the output member (reverse input torque), and so the elastic action of the first elastic member causes centering of the retainer. With the retainer in this centered state, the torque transmission member does not engage with either the input member or the output member, but remains freely rotatable, and consequently the output member is able to slip in a disengaged manner.
The above operation can be achieved by forming a wedge shaped gap between the input member and the output member, and then causing an engagement member which functions as the torque transmission member to engage with, or disengage from this wedge shaped gap. This type of construction includes structures in which the cam surface for forming the wedge shaped gap is provided on either the output member or the input member (and an engagement member with a circular cross section such as a roller or a ball is used), and structures in which the cam surface for forming the wedge shaped gap is provided on the engagement member (and a sprag or the like is used as the engagement member).
The aforementioned restraining means may comprise, for example, a concave engagement section provided on either one of the output member or the stationary member, and a convex engagement section provided on the other member, wherein the engagement section of the stationary member is positioned over the rotational locus of the engagement section of the rotating side, and at each of the prescribed positions the concave engagement section and the convex engagement section engage elastically, thereby restricting the rotation of the output member.
According to such a construction, if the output member is rotated by torque applied to the input member, then at the point where the concave engagement section and the convex engagement section reach opposing positions, the two sections will elastically engage in a circumferential direction, and so rotation of the output member beyond that point is restricted. However, if a large reverse input torque exceeding the rotational restraining force of the restraining means is applied to the output member, then the engagement between the concave engagement section and the convex engagement section releases, and the output member begins to slip freely.
This type of construction can be realized, for example, by providing the concave engagement section on the stationary member, and providing the convex engagement section on the output member with a second elastic member disposed therebetween. In such a case, the concave engagement section and the convex engagement section engage through the elastic force supplied by the second elastic member. If a large reverse input torque exceeding the torque reaction force provided by this elastic force is applied to the output member, then the output member can be caused to slip, and rotate freely.
If the output member and the stationary member are arranged so as to oppose one another in an axial direction, with the concave engagement section and the convex engagement section engage positioned within the opposing section, then the restraining means can be integrated within the structure of the reverse input blocking clutch, enabling a more compact overall device to be produced.
In those cases in which a motor is used as the rotational driving source, then when the concave engagement section and the convex engagement section engage (not only immediately following engagement, but also immediately prior to engagement), the driving current of the motor increases. Consequently, if the motor is stopped at the point when this increase in driving voltage is detected, then the driven member can be accurately stopped at each of the prescribed positions without the use of a sensor.
The rotational resistance application means may comprise a sliding member capable of engaging in a circumferential direction with one of either the retainer or the stationary member, and sliding relative to the other. For example, the sliding member could be provided so as to slide relative to the stationary member while being engaged in a circumferential direction with the retainer.
The driven member could be, for example, a mirror of a vehicle. In such a case, one of the two prescribed positions could be set as a working position in which the mirror protrudes out from the side of the vehicle, and the other position set as a retracted storage position.